The benzodiazepines and opiates are classes of widely used antianxiety and analgesic drugs which affect the nervous system by binding to specific receptors on cell surface membranes and, as a result, appear to influence the synaptic interactions between neurons. The presence of these receptors suggested the existence of endogenous ligands. Opiate peptides have been demonstrated and endogenous benzodiazepine activity has been found in brain extracts. The significance of research related to these drugs is derived from the increased basic understanding of nervous system function mediated by the endogenous compounds, the design of more effective drugs for clinical use and improved drug abuse therapy. Beyond this, it seems reasonable to suggest that understanding the function of endogenous compounds associated with tranquilizing and analgesic actions may provide insight into the nature of certain emotional disorders. The proposed research program will study the development of opiate and benzodiazepine related neuronal systems in primary dissociated cell cultures as models: 1) for the cellular localization of drug related receptors and endogenous peptides, 2) for the study of the influence of interacting neuronal systems on receptor and peptide development, and 3) for the study of the effects of chronic drug treatment on these neuronal characteristics. The cell culture systems to be studied individually or in coculture are the spinal cord, dorsal sensory ganglion, sympathetic ganglion and cerebellum. The relationship between opiate and substance P related neuronal mechanisms will be studied as will the relationship between benzodiazepine and GABA receptor. The receptors will be assayed by radiolabeled ligand binding and localized by autoradiography. Opiate peptide and substance P will be assayed by immunohistofluorescence and radioimmunoassay.